Description
Epidural anesthesia provides localized pain relief by administering an analgesic agent into the epidural space, often using a catheter for continuous infusion. The insertion level of the epidural needle varies based on the dermatomes needing blockage: T8 to T12 for lower abdominal procedures and T3 to T7 for thoracic procedures. The two primary techniques for accessing the epidural space are the midline and paramedian approaches. In the midline approach, the needle is directed between the vertebral spinous processes, whereas the paramedian approach involves inserting the needle 1 cm lateral and caudal to the spinous process at a 35-degree angle. A local anesthetic, usually 1% lidocaine, is injected to minimize discomfort before needle insertion. Confirmation of correct placement in the epidural space is typically achieved through the “loss of resistance” technique, where resistance to injecting saline or air diminishes once the needle passes through the ligamentum flavum. Studies suggest that image-guided techniques, particularly ultrasound, can improve placement efficiency and reduce discomfort, especially in patients with challenging anatomy (17).
Anesthetic agents, delivery methods, and innovations in epidural analgesia
Once the epidural space is confirmed, a flexible catheter is inserted and positioned 4 to 5 cm into the space for medication administration. Testing catheter positioning, via aspiration for blood or cerebrospinal fluid and a test dose of local anesthetic, is essential. Effective bilateral sensory block tests indicate proper catheter placement. A variety of anesthetic and analgesic agents can be injected for epidural anesthesia. Commonly used anesthetics include lidocaine, ropivacaine, bupivacaine, and levobupivacaine, with a trend toward using long-acting agents and potentially liposomal formulations in the future. Numerous dosing regimens are employed in modern practice. Long-acting agents, such as ropivacaine and bupivacaine, are preferred to prevent the block from wearing off too quickly.
It is important to note that the volume administered determines the spread of the local anesthetic within the epidural space, thus affecting the number of dermatomes blocked. In contrast, the concentration of the analgesic influences the block's density and the extent of the motor block. Epidurally administered adjuvant analgesic agents include fentanyl, sufentanil, morphine, clonidine, and steroids.
Modes of epidural drug delivery
Historically, there are two primary methods for administering epidural medication: continuous epidural infusion and patient-controlled epidural analgesia, which can optionally include a continuous background infusion. In patient-controlled epidural analgesia, patients can administer bolus doses with a lockout period to prevent overdose. Evidence shows that patient-controlled epidural analgesia leads to lower local anesthetic consumption and reduced motor block during labor analgesia (47). Additionally, patient-controlled epidural analgesia is associated with less overall anesthetic consumption in surgical patients and improved patient satisfaction (44).
Programmed intermittent epidural bolus, which delivers programmed bolus doses at scheduled intervals, is increasingly being used in labor analgesia. The rationale behind this technique is that repeated bolus doses of local anesthetic can create a more widespread sensory block than continuous administration. A meta-analysis indicates that programmed intermittent epidural bolus combined with patient-controlled epidural analgesia decreases the rate of instrumental deliveries, the incidence of breakthrough pain, and overall local anesthetic usage compared to continuous epidural infusion combined with patient-controlled epidural analgesia (49).
To enhance the effectiveness of labor epidural analgesia, the dural puncture epidural technique has been suggested. In this method, the dura is intentionally punctured with a spinal needle. Although identifying loss of resistance can be subjective, this technique provides a clear endpoint when cerebrospinal fluid returns through the spinal needle. The dural puncture may facilitate the transfer of local anesthetic into the subarachnoid space, thereby accelerating the onset of analgesia. However, evidence regarding the efficacy of this technique is conflicting. One randomized controlled trial involving obese parturients compared the dural puncture epidural with the standard epidural and found no significant differences in the quality of analgesia (38).
Indications
Epidural anesthesia serves three primary purposes: perioperative analgesia, labor anesthesia, and pain management for acute or chronic conditions.
In the perioperative setting, it provides regional anesthesia for the lower extremities, abdomen, and thorax during various surgical procedures, often alongside general anesthesia. This combination reduces the need for systemic analgesia and enhances postoperative pain control. Despite alternative techniques and minimally invasive surgeries affecting its popularity, epidural anesthesia remains important, especially for moderate to large thoracotomies and upper abdominal laparotomies. Its role in minimally invasive surgery is debated, as evidence of its superiority over other analgesics is inconclusive.
In labor, epidural analgesia is widely used as the gold standard for managing labor pain in high-income countries, with its use in up to 64% of births. This procedure involves the administration of medication through a lumbar epidural catheter, which is inserted between the L2 and L4 vertebrae. It effectively blocks pain up to the T10 dermatome, offering significant relief during labor. Although epidurals can be associated with side effects such as hypotension, fever, urinary retention, and prolonged labor duration, research indicates that they do not significantly increase the rates of cesarean deliveries. Notably, studies suggest that epidural analgesia may lower the risk of serious childbirth complications by 35%, particularly for women at higher risk due to factors like premature labor or preexisting medical conditions (14).
Beyond obstetrics, thoracic epidural analgesia is an established method for managing acute pain from multiple rib fractures. It has been shown to provide better pain relief compared to systemic opioids, which can improve respiratory function and reduce pulmonary complications. Additionally, thoracic epidural anesthesia is used to manage chronic pain conditions, such as cancer-related pain and complex regional pain syndrome, offering substantial analgesic benefits in these difficult situations (34).
Contraindications
Epidural anesthesia has both absolute and relative contraindications.
Absolute contraindications include:
| • Patient refusal |
| • Local infection at the puncture site |
| • Elevated intracranial pressure with a risk of herniation |
| • Severe coagulation abnormalities |
Relative contraindications. Relative contraindications depend on individual patient factors, provider expertise, and a risk-benefit analysis.
Thromboprophylaxis. The risk of epidural hematoma is a significant concern for patients taking anticoagulants or antithrombotic agents. The American Society of Regional Anesthesia and Pain Medicine provides guidelines on neuraxial anesthesia (15). Aspirin and NSAIDs are not contraindicated for epidural anesthesia.
Guidance varies for other antiplatelet medications and direct-acting anticoagulants. Warfarin is typically held for five days or until the international normalized ratio normalizes, with catheter removal only when the international normalized ratio is less than 1.5. Low molecular weight heparin should be withheld for 12 hours before the procedure and can be resumed afterward (15).
Thrombocytopenia and coagulopathy. Platelet counts above 70,000 are often considered safe for epidural procedures. In cases like immune thrombocytopenic purpura and gestational thrombocytopenia, functional platelets may still be present at lower counts, necessitating careful evaluation of the underlying cause, platelet trends, and bleeding history. An epidural can generally be performed safely with counts above 50,000 (03).
Sepsis. Epidural anesthesia in patients with sepsis has traditionally been approached with caution due to concerns about hypotension and autonomic instability. However, emerging evidence suggests that thoracic epidural anesthesia may offer potential benefits in selected septic patients. Its use in sepsis remains a complex decision, balancing potential benefits in splanchnic perfusion and inflammation modulation against the risks of hemodynamic instability (41).
Preexisting neurologic conditions. Epidural anesthesia in patients with existing neurologic disorders requires careful risk assessment. Published literature indicates that individuals with structural spinal pathology may have a slightly higher risk of developing new or worsening neurologic deficits after receiving neuraxial anesthesia. A review by Crowe and Drew found that the risks were elevated, particularly among those with compressive radiculopathy or multiple neurologic conditions (07).
Preload-dependent state. Epidural anesthesia lowers systemic vascular resistance, which can lead to hypoperfusion in patients with aortic stenosis or hypovolemia. This may compromise coronary perfusion and requires individual assessment.
Outcomes
Epidural anesthesia offers several advantages for postoperative care, including improved pain relief, faster recovery, reduced risk of pneumonia, and lower morbidity and mortality rates, especially when used in conjunction with general anesthesia. Studies continue to underscore these benefits. For instance, a study conducted by Kearns and colleagues found that epidural analgesia during labor reduced severe maternal morbidity by 35%, with even more significant benefits observed in women with medical indications for its use and those experiencing preterm labor (14). Epidural techniques effectively reduce the body's stress response to major surgery, thereby minimizing postoperative complications, such as pulmonary issues, thromboembolism, and cardiac events. Use of neuraxial anesthesia in acute stroke has been described; its use can help avoid the need for general anesthesia in this high-risk patient cohort (36). Furthermore, research indicates that epidural anesthesia improves recovery quality and shortens hospital stays, particularly in high-risk patients undergoing major surgical procedures (37).
Adverse effects
Non-neurologic complications. Although epidural anesthesia offers significant benefits, it is associated with various non-neurologic complications that require careful management. Hypotension remains a common concern, but research emphasizes that it does not necessarily predict postoperative mobility, reinforcing the need for early mobilization to enhance recovery outcomes. Respiratory depression, local anesthetic toxicity, nausea, urinary retention, infection, and pruritus are other well-documented risks, with newer anesthesia techniques helping reduce incidence rates. Studies also highlight that early recognition and intervention for complications like infection and urinary retention can prevent long-term morbidity. Advances in optimized drug combinations have shown promise in minimizing nausea and pruritus, improving overall patient comfort (10).
Neurologic complications. Neurologic complications from neuraxial anesthesia are rare but can be serious. They may arise from vascular injuries, trauma, or infections such as epidural abscesses. Symptoms can overlap with surgical factors, nerve compression, or preexisting conditions, making early identification difficult, especially when postoperative sedation or immobilization hampers assessment. Most symptoms are transient and sensory-related, often resolving on their own without intervention. However, urgent conditions like epidural hematomas, which occur at an incidence of approximately two per 100,000 to one per 140,000 to 220,000 cases, require immediate intervention to prevent permanent neurologic damage. Research emphasizes that following best practices and achieving rapid diagnosis significantly improves patient outcomes (31; 40).
Recovery and prognosis. The outcome for neurologic injuries is generally positive, with most patients experiencing complete recovery. Those at greater risk include patients at extremes of age and those with obesity or diabetes (29; 40).
Neurologic complications can result from a range of direct and indirect mechanisms, as outlined in Table 1.
Table 1. Mechanisms of Neurologic Injury
Mechanism | Description |
Mechanical trauma | Direct injury to nerves by the needle or catheter |
Chemical neurotoxicity | Anesthetic agents or preservatives causing neuronal damage |
Vascular compromise | Ischemia from hypotension, vasospasm, or arterial occlusion |
Bleeding complications | Epidural or spinal hematoma causing compression |
Infectious causes | Meningitis or abscess formation |
Delayed immune reactions | Immune-mediated neuropathies (eg, Guillain-Barre syndrome) |
Anatomical factors | Stenosis, fibrosis, or anomalous spread (eg, subdural or subarachnoid) |
Table 2. Types of Neurologic Complications and Underlying Mechanisms
Neurologic complication | Potential mechanisms |
Radiculopathy | - Nerve root trauma
- Anesthetic toxicity |
Cauda equina syndrome | - Spinal stenosis
- Neurotoxicity
- Epidural air
- Subarachnoid spread
- Epidermoid cyst |
Myelopathy | - Spinal infarction
- Hematoma or abscess
- Arachnoiditis
- Fibrosis
- Drug errors |
High spinal block and coma | - Subarachnoid injection leading to profound block and apnea |
Postdural puncture headache | - Dural puncture
- Pneumocephalus
- CSF leakage leading to intracranial hypotension |
Subdural hematoma or cranial nerve palsy | - Low CSF pressure causing brain sagging or traction injury |
Seizure | - Intravascular injection of local anesthetic |
Bacterial meningitis | - Aseptic technique failure
- Hematogenous spread |
Horner syndrome | - High sympathetic blockade
- Neurotoxicity |
Trigeminal neuropathy | - Cranial spread of anesthetic
- Neurotoxicity |
Guillain-Barre syndrome | - Autoimmune demyelination following immune activation |
Radiculopathy. The most common complication of epidural anesthesia is lumbosacral radiculopathy, which can occur as a single or multiple nerve root condition. It's important to distinguish these complications from other issues, such as focal neuropathy or plexopathy, which may arise from surgical positioning or childbirth. Studies have been investigating the incidence and management of lumbosacral radiculopathy following epidural anesthesia. This condition is a leading cause of low back pain and often affects several nerve roots, resulting in pain localized to the lumbar or sacral dermatomes.
A case report by Giulietti and colleagues examined the effectiveness of using local anesthetics alone for treating radicular pain, demonstrating significant symptom reduction (11). Additionally, a literature review by Muthu and coworkers explored the use of platelet-rich plasma as an alternative to steroids for managing lumbar radiculopathy, showing promising results in achieving sustained pain relief (25). Updated findings indicate that although spontaneous improvement is common, severe cases may necessitate imaging studies or surgical intervention.
Cauda equina syndrome. Severe polyradiculopathies can be associated with spinal stenosis, which may be revealed during epidural anesthesia. Studies continue to highlight the risks linked to epidural anesthesia in patients with preexisting spinal stenosis (02). Cauda equina syndrome may result from injecting fluid into a restricted space or from edema compressing spinal roots. A case report by Magda Tsolaki and colleagues describes a case of cauda equina syndrome due to arachnoiditis following combined spinal-epidural anesthesia during a cesarean section, reinforcing concerns about neurotoxicity caused by anesthetics (20). Rare cases have been attributed to the injection of saline with preservatives (08).
Myelopathy. Acute myelopathy presents symptoms like paraparesis, sensory deficits, and incontinence, with prognosis depending on lesion severity and reversibility. Spinal cord infarction is a rare but serious complication of epidural anesthesia. Patients may lose pinprick and temperature sensations while retaining vibratory and proprioceptive abilities, along with bladder and bowel incontinence, often linked to anterior spinal artery infarcts caused by atherosclerosis, vasculitis, hypotension, or arterial compression from large anesthetic volumes (19). Acute myelopathy can follow a complete spinal block, especially with subdural injections during epidural anesthesia, increasing risks for patients under general anesthesia who cannot be monitored. Guidelines highlight the importance of MRI for early detection and careful anesthetic management in high-risk individuals (09).
Medication errors. Though rare, medication errors can lead to serious complications. For example, Patel and Dexter reported 25 patients who received inadvertent epidural potassium chloride, resulting in paraplegia and potential mortality (28). In a narrative review of 22 reports of tranexamic acid-associated intrathecal toxicity occurring from July 2018 to September 2022, it was found that 36% of the patients died and 19% had permanent harm (27). In contrast, Pysyk and Filteau successfully managed a case of tranexamic acid administration through saline flushing, resulting in no neurologic deficits (30). This case report described an accidental epidural infusion of tranexamic acid, reinforcing the neurotoxic potential of tranexamic acid even at low concentrations and the importance of strict route verification protocols.
Spinal cord compression. Spinal cord compression caused by an epidural hematoma is a neurosurgical emergency that requires prompt imaging, preferably an MRI, to prevent irreversible neurologic damage. Although spinal epidural hematomas are rare, with an incidence of approximately 0.1 cases per 100,000 people, they are increasingly being reported in patients undergoing anticoagulation therapy. The source of the bleeding is typically venous, arising from the epidural venous plexus. Urgent MRI is the preferred diagnostic method. Management includes urgent surgical decompression, as delayed intervention is associated with worse neurologic outcomes (23).
Epidural abscesses. Spinal epidural abscesses are a rare but serious cause of myelopathy, presenting classically with back pain, fever, and neurologic deficits. They can arise from external contamination or a hematogenous source and require immediate MRI and treatment (48).
Misplacement of an epidural catheter. The misplacement of an epidural catheter can result in rare but serious neurologic complications. These may include the formation of sterile inflammatory granulomas, adhesive arachnoiditis, and unintended deposition of anesthetic in the subdural space, which can lead to motor deficits. Although these events are uncommon, their severity requires increased clinical vigilance and timely diagnostic assessment (33).
Coma and high spinal block. Unintended subarachnoid injection during epidural anesthesia can cause a high spinal block, leading to severe hypotension, bradycardia, respiratory compromise, and even coma or cardiopulmonary arrest. This is harder to detect in patients under general anesthesia, and although many regain consciousness within hours, recovery may take up to 24 hours (04). Immediate airway management and hemodynamic support are essential.
Postdural puncture headache and intracranial complications. Postdural puncture headache occurs in about 0.6% of epidural procedures, particularly after an inadvertent dural puncture, with 16% experiencing severe headaches; rarely, air used during the procedure can lead to pneumocephalus (46). Conservative treatments like hydration and caffeine are effective, whereas an epidural blood patch remains the gold standard for persistent cases (42; 01).
Seizures and local anesthetic systemic toxicity. Intravascular injection of local anesthetics can cause local anesthetic systemic toxicity, with early signs like perioral numbness and tinnitus potentially progressing to seizures and cardiovascular collapse. Immediate airway management and intravenous lipid emulsion therapy are essential treatments (26; 24).
Bacterial meningitis. Bacterial meningitis is a rare but serious complication resulting from contamination during catheter insertion or hematogenous spread. Symptoms include fever and neck stiffness, requiring prompt broad-spectrum antibiotic treatment (16).
Horner syndrome. Horner syndrome can occur during high thoracic or cervical epidurals, presenting as unilateral ptosis, miosis, and anhidrosis. It is generally benign and resolves within hours (22).
Trigeminal neuropathy. Trigeminal neuropathy is a rare but acknowledged complication that can arise after epidural or spinal anesthesia. Patients usually exhibit facial numbness or tingling sensations, which typically resolve within several weeks. The precise mechanisms behind this condition are not completely understood, but they may involve the unintended spread of the anesthetic agent or intracranial hypotension, which can lead to nerve traction (21).
Guillain-Barre syndrome. Guillain-Barre syndrome is a rare complication that can occur in patients 1 to 2 weeks after receiving epidural anesthesia. Patients may have an increased risk of developing Guillain-Barre syndrome due to a possible interaction between the anesthetic and the myelin or from nerve trauma caused by the needle or catheter. These factors can trigger immunological processes that lead to neuropathy (05; 18). Understanding these risks is crucial for ensuring patient safety in clinical settings.
Special considerations
Although anesthesiologists typically perform epidural anesthesia, neurologists should be aware of the following patient populations undergoing this procedure due to these patients’ specific considerations.
Pregnant patients. Approximately half of the epidural anesthesia procedures in academic medical centers are administered to pregnant women during labor and delivery. Studies confirm that neurologic complication rates in pregnant patients are comparable to those in nonpregnant patients (43; 45). However, the complications tend to be less severe in pregnant patients, likely due to the absence of comorbidities that are often present in nonpregnant populations. Additionally, general anesthesia can obscure early signs of complications, potentially leading to increased risk for serious injuries.
Myasthenia gravis. Patients with myasthenia gravis pose unique challenges for anesthetic management due to impaired acetylcholine receptor function, which increases sensitivity to neuromuscular blocking agents and raises the risk of perioperative respiratory complications. The physiological stress of surgery can precipitate a myasthenic crisis, making careful preoperative assessment and intraoperative monitoring essential. Reversal of neuromuscular blockade is particularly complex in patients receiving acetylcholinesterase inhibitors; however, evidence supports the use of sugammadex as a safe and effective agent to mitigate residual paralysis (13). Regional techniques, such as epidural or combined spinal-epidural anesthesia, have been shown to reduce the need for mechanical ventilation and decrease postoperative opioid consumption (12).
Multiple sclerosis. Historically, multiple sclerosis was considered a relative contraindication for epidural anesthesia due to potential neurotoxicity and the risk of relapse, particularly in women of childbearing age. However, research by Shakeri and colleagues further supports the safety of epidurals during labor for patients with multiple sclerosis (35).
Acute inflammatory demyelinating polyneuropathy. Acute inflammatory demyelinating polyneuropathy, or Guillain-Barre syndrome, is rare but has been documented in pregnancy. The lack of randomized trials has hindered the establishment of guidelines. Yet, case reports and a literature review indicate that epidurals are generally well tolerated in patients with acute inflammatory demyelinating polyneuropathy, emphasizing the importance of individualized clinical judgment in these cases (05).
By keeping up with emerging literature and best practices, healthcare professionals can improve their understanding and management of epidural anesthesia in these specific populations, ultimately leading to better patient outcomes.
